Variable injection dephasor



Nov. 18, 1958 P. A. RIBAUX VARIABLE INJECTION DEPHASOR Filed Oct. 18, 1956 PAR/BAL/X IN VENTOR. 54 2h ATTORNEYS ter.

United States Patent 2,860,619 VARIABLE INJECTION DEPHASORF Paul A. Ribaux, Wayne, Mich., assignor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Application October 18, 1956, Serial No. 616,709

4 Claims. (Cl. 123139) The application deals generally with internal-combusstroke of the free-piston engine, and consequently the' position of the pistons at inn'er dead center, is variable. Accordingly, it is an object of my invention to provide a fuel injection system for a free-piston engine that provides fuel injection at the proper time so that the engine runs quietly and smoothly.

Another object is to provide a fuel-injection system wherein the time of fuel injection may be varied as the engine load changes.

These and many other objects will become apparent after reading the following specification and drawings wherein:

Figure 1 is a schematic representation of a fuel injection system utilizing my invention in'conjunction with a free piston engine.

Figure 2 is a section of one embodiment of the dephasor,

Figure 3 is a section of another embodiment, and

Figure 4 is a section taken along line 4-4 of Figure 3.

Most diesel engines in use today use the jerk type injection system. In this system, the pump, which is driven in synchronism with the engine, meters and delivers to the injector the exact quantity of fuel needed for each cycle. Due to the finite time required for the pressure wave to travel through the tubing connecting the fuel pump to the injector, there is a slight time delay between the start of delivery by the pump and the injection. For a given length of tubing, this time delay remains constant over the entire range of operation.

If the jerk-type system were to be used in conjunction with the free-piston engine, the pump must, of necessity, be connected in some suitable manner to the piston synchronizing mechanism since this is the only member available as fuel pump drive whose position is directly related to the piston position. However, the syn chronizing mechanism does not rotate continuously as does the cam shaft in other engines; instead it oscillates, coming to a full stop and reversing its motion each time the pistons reach and pass through inner and outer dead center. Therefore, if the jerk-type system is used the fuel delivery must be terminated before inner dead cen- Because the piston velocity rapidly decreases as it approaches inner dead center, this last part of the cycle cannot be easily used because the velocity of the piston synchronizing mechanism is too low for proper injection. 011 the other hand, if the injection takes place earlier in the cycle rough, noisy operation andlow operating eificiency results. One solution to this problem would be to insert a very long delivery tube between the fuel pump and the injector. This would be suitable for engines which operate at relatively uniform loads, but if the engine is to be used in an automobile in which it would operate in the entire range between idle and full load, the system would be unsatisfactory because, as explained above, the position of inner dead center and the frequency of operation would change. The delay inherent in a tube length selected to operate at idle would be much too long for full load operation.

Referring to Figure 1; it is seen that inthe instant invention a dephasor 11 is interposed between the fuel pump 12 and the injector 13 which delivers the fuel to the combustion chamber 14 of the free piston engine 15. This dephasor consists of a generally cylindrical body 20 having a longitudinal cavity therein. An inlet connection 21 is formed in the cylinder wall near the mouth of the cavity, and an outlet connection 22 is located at the bottom of the cavity. A hollow core 23 having a spiral groove 24 along its outer wall fits snugly within the cavity so that the first flight of the spiral groove is adjacent to connection 21 and the last portion of the groove is adjacent to connection 22. At each level or flight of spiral groove 24 a radial hole 25 entering into the hollow interior of core 23 is formed in the wall of this core. A shaft 26 fits within core 23 while an upper necked portion 27 in this shaft is aligned with inlet 21 and hole 25 which extends through the first level of groove 24. A spiral groove 28 leads from necked portion 27 and ex tends along the outer surface of shaft 26. A cap 29 fits over the mouth of the cavity to seal it. However, an ex- I tension 30 of shaft 26 extends through a suitable opening in cap 29 so that this shaft may be rotated within core 23 by turning extension 30 which is preferably linked into the control system of the engine although it may be operated manually, I 1

The dephasor functions in the following manner. The fuel entering at 21 divides when it reaches the first flight of spiral groove 24, a portion flows along this spiral to the outlet, another portion flows into the recess formed between the necked portion 27 of the shaft and the inner wall of core 23 and thence to groove 28 since this recess is always connected to the groove 28. Depending upon the angular position of the shaft within the core this groove 28 will connect with a particular radial hole 25 in the core and the fuel will flow through this preselected hole back into spiral groove 24 andthence to the outlet. It is apparent, therefore, that if this groove 28 connects to a hole 25 at the last level, a portion of the fuel will flow along short groove 28 and will traverse its flow path quickly, that is, the injection delay will be relatively short. If on the other hand, this groove 23 connects with a hole 25 in the first flight of groove 24, the flow time through the shortened path will be almost as long as if the fuel were flowing along the entire length of groove 24 resulting in a longer delay. Depending on the engine load, the operator may vary the position of the shaft within the core and thereby change the flow delay time in a stepwise manner to suit the engine-load conditions.

Figures 3 and 4 show a different embodiment of my invention wherein the injection time may be varied continuously. In this modification, a short, hollow, cylindrical body 40, closed at both ends, has an inlet 41 through its front face and an outlet 42 through the rear face. Within the hollow interior of body 40 is positioned a control disc 43 which may 'be rotated by means of shaft 44 Patented N ov..- 18,- 1958.

which is rigidly connected to the center of disc 43 and projects through a suitable opening in the front face of body 41). Matchin'g circular grooves 45 are formed on both the obverse .and the reverse faces of disc 43, these grooves extend somewhat less than 360 around the disc as can be seen in 'Figure 4. An aperture 46 extends through disc 43 and connects one pair of the endsfof matching grooves 45. The flow path isthroug'hdrile't 41 along groove '45 on "the obverse of disc 43, through aperture 46,'alon'g reverse groove, 45, and through outlet 42. By rotating disc 43, it is possible to align inlet d1 with any portion of groove '45 on the obverse of disc 43; when the inlet is adjacent to that portion of groove 45 which connects .to aperture '46, the flow path and consequently the injection delay time will be relatively short. Conversely, 'if the inlet is adjacent to that portion of the groove remote from aperture 46, the injection delay time will be longer. "In order to lengthen the injection delay time one could, of course, connect as many discs in series as is'necessary.

Having thus fully described my invention, I claim:

1. A fuel'injection system for an internal combustion engine which comprises; a fuel injection nozzle, a fuel pump having a delivery port, fuel tubing connecting the delivery'port of said pump 'to said 'fuel injection nozzle, a dephasor'in said fuel tubing, the dephasor having aninlet connected to the'delivery of said pump and an outlet connected'to said fuel injec'tion' nozzle, said dephasor comprising a hollow body open at one end, a tubular core within :said hollow body 'fittingly engaged with the inner walls of said 'body, a generally spiralgroove along the surface ofisaid core in engagement with said body, said groove and said body together forming a fluid path of fixed len'gth through said dephasor, said core including a plurality of radial holes connecting selected points on said fluid .path with the interior of said core, a shaft having a generally spiral groove along its length rotatably fitted within said tubular core, said second named spiral groove being substantially shorter than said first named groove, said first named groove and said second named groove both connected to said inlet and said first named groove only connected to said outlet, whereby said second named spiral groove may be aligned with a predetermined radial hole in said tubular coreby rotation of said shaft to selectively alter the efiective length of said first named groove.

2. A fuel injection system for an internal combustion engine which comprises; a fuel injection nozzle, a fuel pump, a fuel conduit between said pump and said nozzle, a dephasor having an inlet connected to said pump and an outlet connected to said fuel injection nozzle, said dephasor comprising a hollow body, a rotatable disc within said body, a pair of matching, interconnected, grooves on opposite faces of said disc, said inlet being adjacent to one of said grooves and in alignment therewith, said outlet being adjacent to the other of said grooves and in alignment therewith, so that the effective length of said 4. In a fuel injection system for an internal combus tion engine having a fuel pump, a fuel injection nozzle and a fuel tube connecting said nozzle and said pump, a dephasor in said fuel tube, said dephasor comprising a body having a fixed inlet connected to the delivery of said pump and a fixed outlet connected to said fuel injection nozzle, said dephasor having an internal .flo w path positioned therein and connected to said inlet and said outlet, rotatable means containing a portion of said flow path positioned within said dephasor body for varying the effective length of said fuel .flow path upon totation thereof.

ReferencesCited in the file of this patent UNITED STATES PATENTS 1,365,301 Brooks Jan. 11, 192 1 FOREIGN PATENTS 539,116 Great Britain Aug. 28, 1941 

